There has heretofore been used generally a fluorocarbon gas and particularly a dichloro-difluoromethane (hereinafter referred to as a CFC12) as a refrigerant for an air conditioning apparatus or cooling means in an automobile and so on. However, since it has become apparent that the CFC12 has exerted bad influences upon human health in that it destroys the ozonosphere to thereby cause skin carcinomas, an application of the CFC12 has been restricted. Then, a trifluoro-monofluoroethane (hereinafter referred to as a HFC134a) being less destructive of the ozonosphere is considered as a replacement thereof.
While it is urged to confirm the safety of the replacement gas as soon as possible, it is increasingly expected that measures for conveying the gas works in safety and without any maintenance thereof. Conventionally, such a hose as illustrated in FIG. 1 is used as a hose for conveying a refrigerant gas such as a fluorocarbon etc. The refrigerant conveying hose comprises an inner tube 1 made of a synthetic resin, an intermediate rubber layer 5 adhered to on the inner tube 1 through an adhesive 3, a fiber reinforced layer 7 provided on the outer periphery surface of the intermediate rubber layer 5 and an outer tube 9 provided on the fiber reinforced layer 7.
Referring to each material of the above hose in which a fluorocarbon gas is employed as a refrigerant, the inner tube 1 is formed of a resin material with an excellent refrigerant-impermeability such as a polyamide resin (PA), the intermediate rubber layer 5 is formed of a isobutylene-isoprene rubber (IIR) or a chlorinated isobutylene-isoprene rubber (CI-IIR) each having a good moisture-impermeability and refrigerant-impermeability, the fiber reinforced layer 7 is formed of a polyester fiber, a rayon fiber or a nylon fiber etc., and the outer tube 9 is formed of a chlorinated butyl rubber (CI-IIR), an ethylene propylene diene monomer rubber (EPDM) or a chloroprene rubber (CR) etc. each having a good oil resistance and weathering resistance.
Such a refrigerant conveying hose is manufactured, for example, according that the above layers are sequentially laminated one by one as below.
(a) A synthetic resin for the inner tube 1 is extruded over a mandrel of made a rubber or resin material by an extrusion molding machine to thereby form a tubular body. After an adhesive applied to on the inner tube 1 is devolatilized, the intermediate rubber layer 5 is molded through the extrusion molding machine.
(b) Next, the fiber reinforced layer 7 is provided on the intermediate rubber layer 5 by measures of a braid or spiral knitting of reinforcing fiber threads.
(c) After a prescribed adhesive is applied to the outer periphery surface of the fiber reinforced layer 7 as formed above, the outer tube 9 with a predetermined wall thickness is molded thereon through the extrusion molding machine.
(d) At last, the resulting laminated tube is subjected to a steam vulcanization under the condition that a vulcanizing temperature and time are usually around 150 to 160.degree. C. and 30 minutes to one hour, respectively.
Because the inner tube 1 is made of a polyamide resin (PA), the above laminated tube is largely improved in respect of a refrigerant-impermeability, as compared with anther conventional laminated tube using an acrylonitrile-butadiene copolymer rubber (NBR) or a chlorosulfonated polyethylene rubber (CSM) as a material of the inner tube 1. However, since a polyamide resin material has a high rigidity, there is a problem that the resulting tube lacks a necessary flexibility. On the other hand, when the thickness of the wall of the inner tube 1 is made thinner in order to take on a sufficient flexibility, there happens another problem that a refrigerant-impermeability to be targeted is not attained.
As each material of the intermediate rubber layer 5 and the outer layer 9, the chlorinated butyl rubber (CI-IIR) and the ethylene propylene diene monomer rubber (EPDM) are used respectively, which involves the vulcanizing process to eventually reduce the yield and raise the manufacturing cost. This hose includes a laminated body of the different materials such that the inner tube 1 and the intermediate rubber layer 5 are made of the resin material and the rubber material respectively, therefore it causes a problem that the hose, as it is, could not be recycled. Further, the vulcanizing process, being indispensable due to an employment of the rubber layer, breeds the necessity of an additional treatment for preventing the reinforcing fiberthreads fromshrinking. Conventionally, as measures for preventing the shrinkage, a shrinkage-reducing treatment such as a heat-setting and so on has been carried out. Meanwhile, there exists another problem that an increasing demand for lightening of the hose in recent years is not necessarily satisfied because of use of the rubber layer.
Accordingly, the present invention is directed to overcome the above-mentioned deficiencies inherent to the conventional refrigerant conveying hose, and an object of the present invention is to provide a refrigerant conveying hose intended to get lightened in weight wherein the flexibility is improved than ever while the excellent refrigerant-impermeability remains unchanged.
Another object of the present invention is to provide a refrigerant conveying hose which has no laminated structure of deferent kind of materials to thereby get recyclable.
An even further object of the present invention is to provide a refrigerant conveying hose intended to get reduced in a manufacturing cost wherein the extrusion molding process is simplified by using the same kind of materials.